Galvanized coatings consisting essentially of zinc are traditionally used for their high level of protection against corrosion, in the automotive industry or in construction, for example. However, these coatings cause solderability problems and are now facing competition from zinc coatings containing magnesium.
Indeed, the addition of magnesium significantly increases the resistance to pitting corrosion of these coatings, which can help reduce their thickness and thus improve their weldability or even maintain the coating thickness and increase the guarantee of protection against corrosion over time.
In addition, corrosion resistance is improved so much that it is now possible to reduce or even eliminate the use of secondary protection measures such as the use of waxes or sealants in places where corrosion is most likely to occur.
However, steel coils with such surface coatings can sometimes stay in storage warehouses for several months and this surface should not be altered by the appearance of surface corrosion before being shaped by the end user. In particular, no initial corrosion should appear regardless of the storage environment, even in cases of exposure to the sun and/or a humid or saline environment.
The standard galvanized products are also subject to these constraints and are coated with a protective oil that is generally sufficient.